
def interpolate_exponential(y1, y2, mu, exp = 1):
    '''Exponential interpolate `y1` and `y2` with `mu` normalized ``[0, 1]``.

    Example::

        >>> mathtools.interpolate_exponential(0, 1, 0.5, 4)
        0.0625

    Set `exp` to the exponent of interpolation.

    '''

    return (y1 * (1 - mu ** exp) + y2 * mu ** exp)

